Control system



Feb. 11, 1941. A. M. TROGNER 27,231,174

CONTROL SYSTEM Filed Oct. 31, 1939 L5 U" 75 E FILTER A 6 7L 2] 28 FILTERB /}0 3/ DEVICES CONTROI I m BY RELAY E :L. .r l

g E :1. E2 E g ZFILTERA" z FREQUENCY .CONTROL FREQUENCY E :1. 2-- 5 EFILTER "a" g INVENTOR Arthur M-Trugner FREQUENCY Z ATTbRNEY PatentedFeb. 11, 1941 PATENT OFFICE CONTROL SYSTEM Arthur M. Trogner, EastStroudsburg, Pa., assignor to Wired Radio, Inc., New York, N. Y., acornotation of Delaware Application October 31, 1939, Serial No. 302,106

7 Claims.

This invention relates to control systems responsive to frequency, andmore particularly to systems employing a frequency-responsive relaycircuit; for example, the systems disclosed by the present applicant inPatent No. 1,949,590, issued March 6, 1934; and Patent No. 1,972,501,issued September 4, 1934.

In such systems a Signal or impulse of given frequency is sent to acontrolling device which is adapted to respond to that frequency andthereby provide a desired control of other apparatus. However, itsometimes happens that extraneous impulses containing the controlfrequency, or impulses of a transient nature, cause faulty and undesiredoperation.

The main object of this invention is to make a control system selectivebetween a control frequency alone and an impulse or band of frequenciescontaining the control frequency.

A related object is to make a control system responsive to a givenfrequency, only when that frequency is not accompanied by otherfrequencies or impulses A further object is to nullify the effects ofex- 5 traneous impulses on a frequency-responsive relay circuit.

These and other objects are accomplished, in the main, by providing anadditional controlling device which is responsive to frequencies other30 than the control frequency but is not responsive to the controlfrequency, and by making the control of other apparatus dependent uponnonoperatlon of said additional device.

The invention will be more clearly understood 35 from the followingdescription of one illustrative form thereof in connection with theaccompanying drawing in which:

Fig. 1 is a diagram of a preferred embodiment of the invention; and

40 Figs. 2 and 3 are attenuation curves of filters A and B,respectively, in Fig. l.

In the drawing, reference character 5 indicates an ordinary electricpower circuit or branch thereof. Filter A has its input connected tocir- 5 cult 5 and has its output connected to a sensitive relay 6. If itis desired that such relay be a direct current or a polarized type, arectifier 1 is connected between the filter and relay.

In accordance with the invention, a second 50 filter B also has itsinput connected to circuit 5 and has its output connected to a secondsensitive relay 8, through a rectifier 9 if desired. The back contactIII of relay 8 is connected by a conductor H to the front contact I! ofrelaylthus 55 providing a normally closed contact and a normally opencontact, respectively, in a series circuit. This circuit begins withconductor [3 (which is connected to one side of power circuit 5) thencethrough conductor l4, armature I5 of relay 8, contact l0, and conductorII, to 5 contact l2 where the circuit normally is open between contactl2 and armature iii of relay 6; thence by conductor IT to a controlrelay l8, from which the circuit returns through a condenser l9 andcurrent limiting resistance 20 to the other 10 side of power circuit 5.

The normally closed back contact 2| of relay 6, together with armaturel6 thereof and conductor ll, short-circuits the coil of relay I8 whenrelay 6 is not energized. A hold-in circuit for 15 relay I8 is providedfrom conductor 13, through conductor 23 to armature 24 and front contact25 of said relay where the hold-in circuit normally is open. When relayI8 is energized this circuit is completed through the relay coil, con-20 denser l9, and resistance 20 to power circuit 5.

Another armature 21 of relay i8 is connected to conductor 23 and isadapted to close a control circuit through front contact 28 andconductor 29 to controlled devices 30, the control 25 circuit beingenergized through conductors l3 and 3! which are connected to oppositesides of power circuit 5. Devices 30 may be anything controllable byelectric power, such as motors, power relays, switches, lamps, heaters,etc. or control 30 mechanisms such as described in the patents abovementioned.

In operation, the control of devices 30 is effected as follows: Acontrol frequency or signal which may be, for instance, 3,000 cycles, issuperposed on the power circuit 5 at the central station or other remotecontrol point and is received at filter A. This filter readily passesthe control frequency or a narrow frequency band, but highly attenuatesall other frequencies, as illustrated in Fig. 2. The received controlfrequency, after being rectified, energizes relay 6 thereby operatingarmature 16 to close the series circuit (above described) whereby relayI8 is energized. Energization of relay l8 operates armature 24 to close5 its hold-in circuit (above described) thereby holding the relay closedand relieving armature l6 and contact ll of that function. At the sametime, armature 21 closes the control circuit (above described), therebysupplying power to the devices 30.

It will be observed that the received control frequency is alsoimpressed on filter B, but its attenuation curve as shown in Fig. 3 issuch that the control frequency is not capable of passing through thefilter so as to energize relay 8. However, frequencies either higher orlower than the control frequency can pass through filter B and operaterelay 8. Hence, in the event a band of frequencies, transient current,or an extraneous impulse is received (such as is capable of operatingrelay 6 in spite of the selective nature of filter A), relay 8 willattract its armature I5 and thereby open the series circuit at contactIll before relay 6 has time to close said circuit at contact I2. Suchoperation of relay 8 prevents energization of relay I8 and thus preventsundesired or accidental operation of the system even though a receivedimpulse contains the control frequency among others. If, however, theproper control frequency alone is impressed on filter A and operatesrelay 8, a subsequent impulse operating relay 8 through filter B willhave no effect, because the hold-in circuit of relay I8 will then beclosed and will keep relay I8 energized as long as the proper controlfrequency is present on power circuit 5.

When the control frequency ceases, armature I 6 of relay 6 drops backand closes back contact 2I, thereby short-circuiting the coil of relayI8 as described above. This de-energizes relay I8, whereupon itsarmatures 24 and 21 open their contacts at 25 and 28, respectively, andthe control power is removed from devices 30.

It is apparent from the above that only the proper control frequencyalone is capable of causing relay I8 to operate, inasmuch as relay 8 isresponsive to all other frequencies Which may cause faulty or accidentaloperation of relay 8.

It may be desirable, in some cases, to provide a slight time delay onrelay 6 in order to be sure that relay 8 operates more quickly, butordinarily this is not necessary because relay 8 has only to open itsback contact ID to prevent operation of relay I8, whereas relay 6 has tomove its armature I6 all the way to contact I2 in order to energizerelay I 8.

While a preferred embodiment of the invention has been shown anddescribed, it is to be understood that the invention is susceptible ofuse in many control systems and with various modifications within thescope of the appended claims.

What is claimed as new and original to be secured by Letters Patent ofthe United States is:

1. A relay system comprising, a first relay and a second relay, acircuit for energizing said relays, a first filter connected betweensaid circuit and first relay to prevent operation of the latter exceptby current of substantially a given frequency, a second filter connectedbetween said circuit and second relay to permit operation of the secondrelay by currents above and below the given frequency but to preventoperation thereof by current of substantially the given frequency, and acircuit controlled by said relays, said circuit including contacts ofboth relays connected in series.

2. The combination defined by claim 1, and means for nullifying theeffect of said second relay in the event of prior operation of saidfirst relay.

3. In combination, a circuit comprising a normally open contact, anormally closed contact and a current operated device all connected inseries, means for closing the first contact in response to a givenfrequency to energize said device, and means for opening the secondcontact in response to frequencies other than the given frequency butnot in response to the given frequency alone, whereby the latter meansprevents energization of said device in response to a. band offrequencies including the given frequency.

4. The combination defined by claim 3, including an arrangement foropening the second contact prior to closing of the first contact inresponse to a band of frequencies.

5. The combination defined by claim 3, and a hold-in circuit for saidcurrent operated device whereby opening of the second contact while thefirst contact is closed has no effect on said device.

6. The combination defined by claim 3 comprising in addition, means forcontinuing the energization of said current operated device afterinitial closure of said first contact, and means for de-energizing saiddevice upon cessation of the given frequency.

7. In a control system the combination of, a first control meansresponsive to a given frequency, a second control means responsive tofrequencies other than the given frequency but not responsive to thegiven frequency, a device controlled by both said means whereby saiddevice is actuated only in response to the given frequency alone, andmeans for nullifying the effect of one of said control means in theevent of the prior operation of the other of said control means.

ARTHUR M. TROGNER.

